This invention relates to a method and system for terminating the supply of fuel to an engine during a vehicle crash.
In a vehicle accident, it is desirable to cutoff fuel to a vehicle engine. One current system employs an inertia switch that detects sudden changes in vehicle velocity in a single direction. When the vehicle suddenly changes velocity, the inertia switch detects this change as an accident and shuts off fuel to the vehicle engine.
The current system provides limited information about the nature of the accident and may activate at less than optimal moments of vehicle operation. That is, the fuel could be shut off, when no need was truly experienced. Of course, the fuel being shut off for a minor accident, or an accident in a direction unlikely to raise concerns of leaking fuel, would be undesirable. A need therefore exists for a fuel cutoff switch system that obtains greater information about the vehicle crash to provide enhanced performance of the system.
The fuel cutoff switch method and system obtains information from a plurality of sensors. The fuel safety system comprises a fuel system of a vehicle and a fuel cutoff switch that controls the transmission of fuel through the fuel system. A first sensor detects a value related to velocity of the vehicle along a first path. A second sensor detects a value related to velocity along a second path transverse to the first path. A control unit combines the detected values and activates the fuel cutoff switch based on a comparison of the combined detected values with a threshold. This system accordingly provides a greater amount of information than provided by the prior fuel cutoff switch, which detects changes in velocity only along one path. By examining the combination of detected values, the system examines the total energy experienced by the vehicle in an accident. This analysis is particularly useful for front impact events.
The system may combine the detected values through their summation. Moreover, to avoid inadvertent activation of the fuel cutoff switch, the detected values may be modified by a dampening value. This modification may simply be a subtraction of the dampening value from the detected values.
Additionally, the system may compare the combined detected values with a second threshold for rear impact events, which is lower than the first threshold. The system detects the direction of velocity along the first path. In this way, the system may distinguish between front-end collisions and rear-end collisions. When the system detects a rear end collision, the system activates the fuel cutoff switch based on a comparison the detected value relating to velocity along the first path with the second threshold.
The system is also useful in the activation of the fuel cutoff switch in side collisions. The combined detected values are compared with a third threshold for such collisions. The system compares the detected value relating to velocity along the second path with the third threshold. The system need not determine the direction of the side impact since the effect on the vehicle tends to be the same. The fuel cutoff switch is then activated based on this comparison to this third threshold.
The system may thus employ a number of thresholds to examine the type and severity of the event to determine whether an accident has occurred requiring the activation of the fuel cutoff switch. The system detects a value related to velocity of a vehicle along a first path, detects a value related to velocity of the vehicle along a second path transverse to the first path, combines the detected values, and modifies the detected values by a dampening value. Based on the comparison of these detected values with various thresholds, the system may use different thresholds to activate the fuel cutoff switch for front, side, and rear impacts. Moreover, the use of the dampening value allows activation of the fuel cutoff switch for only sufficiently serious accidents that require fuel supply termination.